1. Field of Invention
This invention belongs to the field of semi-synthetic organic chemistry, and provides an advantageous process for isolating certain carbacephem intemediates. This process provides the desired enantiomerically pure .beta.-lactam compounds in high yield, as well as in high chemical purity through an economical and efficient isolation process.
2. State of the Art
An important clinical trial candidate, (6R, 7S)-7-(R)-phenylglycylamido-3-chloro-1-azabicyclo[4.2.0]-oct-2-ene-8-one-2 -carboxylic acid (loracarbef), claimed in U.S. Pat. No. 4,708,956, may be synthesized by various routes. The known synthetic routes involve multiple, complex steps, necessitating efficient, high yielding steps to maximize the overall yield of loracarbef. An object of the present invention is to provide an efficient isolation method, suitable for large scale production, which will assure 100% enantiomeric purity as well as high yields of key .beta.-lactam intermediates. Chemical enantiomeric isolation methods have been reported; however, the yields from the process are unacceptably low. C. C. Budurow, et. al., "An Enantioselective Synthesis of Loracarbef", 30 Tetrahedron Letters 2321 (1989). The improved isolation method of this invention assures 100% enantiomeric purity with yields greater than 95%.